Question regarding Nexus 5K/2K Mixed Dual/Single homed Topologies

[shanemoss]

Hi Folks,

The following document outlines the various options for Nexus 5K/2K topologies;

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/layer2/513_n1_1/b_Cisco_n5k_layer2_config_gd_rel_513_N1_1_chapter_01001.html

Are there any reasons why I couldn't/shouldn't go with a mix of single homed fabric extender with VPC and dual homed fabric extender with VPC on the same hardware.  Specifically the same two 5Ks with some FEXs attached to both and some single homed?

Thanks in advance,

Shane.

[Marwan ALshawi]

Is this mentioned somewhere ?

You can use mix but it's gonna add some complexity to the design and troubleshooting while if you keep it consistent will be simpler

Hope this help

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[Leo Laohoo]

From what I understand, Cisco is starting to change their "recommendation" regarding dual-homing FEX to two (or more) upstream 5K.  You can run multiple uplinks to a single 5K and enable vPC.  The so-called dual-homing is no longer recommended as not only will it cause issues with troubleshooting in the future but can open cases of network instability, such as "split brain".

For redundancy purpose, Cisco is recommending this way:

1.  vPC your 5K;

2.  Each FEX has multiple links towards the 5K in a vPC;

3.  Servers have 2 (or more) NICS and each NICs go to different FEX.

[Marwan ALshawi]

I don't think multi homed 2k to 2x 5k is not recommended !!

This is currently supported with what's called enhanced vPC

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/layer2/513_n1_1/b_Cisco_n5k_layer2_config_gd_rel_513_N1_1_chapter_01010.html

Split brains can be avoided with vPC peer link, keep alive and some other new nx-os features built for this purpose when a good design put in a place

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